The present invention relates to an apparatus for the film formation of a semiconductor, a metal or the like which includes the step of irradiating the surface of a substrate with photon energy in case of forming a desired film.
In view of the situation in which the manufacturing processes of large scale integrated circuits (LSI's) have become smaller with smaller feature sizes, attention has been paid to a photo-induced process in which a substrate surface is formed with a thin film by irradiating it with a photon beam to induce a gas phase chemical reaction or a substrate surface reaction. The main reasons the photo-induced process appears promising are the realization of a low temperature process, the reduction of damage to a substrate, and excellent spatial selectivity of the reaction, i.e., the film formation reaction proceeds on only the substrate surface irradiated with the photon beam. According to a known example obtained by a film formation experiment using a photon beam (Nikkei Electronics, Feb. 15, 1982, page 122), it is claimed that, when a substrate is exposed to a reactive gas and the surface of the substrate is thereafter irradiated with a focused laser beam in the state in which a reaction chamber is evacuated to a high vacuum, a molecular layer adsorbed to the substrate is decomposed to form the nucleus of a reaction product on the substrate surface, and that, when the substrate surface is subsequently irradiated with the unfocused laser beam in the state in which the reaction chamber is filled with the reactive gas, the growth of a film proceeds on the nucleus. This first known example is developed into the second known example disclosed in Japanese Patent Application Laid-open No. 59-40525. In this second known example, a substrate surface is irradiated with the first light to form an area serving as the nucleus of film formation, whereupon the second light having a wavelength suited to the film formation is projected into a reaction chamber to selectively form a film on the nucleus.
In both the known examples, the method in which the photon energy of a laser or the like is projected is adopted in the course of the film formation. As such a light source for inducing the film formation reaction, an excimer laser of ArF or the like having a high intensity in the ultraviolet region is suitable. The excimer laser, however, has had the problems that it is expensive, that the power lowers gradually with operation, and that the laser gas must be exchanged at regular intervals.